MOLYBDENUM ABSORPTION, EXCRETION, AND RETENTION STUDIED WITH STABLE ISOTOPES IN YOUNG MEN AT 5 INTAKES OF DIETARY MOLYBDENUM

A study of molybdenum absorption, excretion, and balance was conducted in four young men fed five amounts of dietary molybdenum, ranging fro m 22 to 1490 mu g/d, for 24 d each. The study was conducted to obtain scientific data on which to base a recommendation on dietary molybdenu m intake for healthy young men. Stable isotopes of molybdenum were use d as tracers. Mo-100 was fed five times during the study and Mo-97 was infused three times. Mo-94 was used to quantify the molybdenum isotop es and total molybdenum in urine, fecal collections, and diets by isot ope dilution. Adverse effects were not observed al any of the dietary intakes. Molybdenum was very efficiently absorbed, 88-93%, at all diet ary molybdenum intakes, and absorption was most efficient at the highe st amounts of dietary molybdenum. The amount and percentage of molybde num excreted in the urine increased as dietary molybdenum increased, s uggesting that molybdenum turnover is slow when dietary molybdenum is low and increases as dietary molybdenum increases. We conclude from th ese results that dietary intakes between 22 and 1500 mu g/d by adult m en are safe for greater than or equal to 24 d and that molybdenum rete ntion is regulated by urinary excretion. Molybdenum is conserved at lo w intakes and excess molybdenum is rapidly excreted in the urine when intake is high.